1. Field of the Invention
This invention relates to reducing hydrolysis of hydrocarbon streams such as crude oil that are subjected to processing at elevated temperatures and, more particularly, to reducing hydrolysis and the subsequent production of hydrochloric acid by the addition of hydrolysis inhibitors to such streams.
2. Description of Prior Art
A typical refinery includes a tank farm or storage area where feed stocks, e.g., crude oil, shale oil, coal oil and certain intermediate hydrocarbon streams from the refining processes are stored for optimum utilization in the refinery. It is not uncommon for these feedstocks to contain chloride salts, primarily metal chloride salts and, more particularly, chlorides of alkali and alkaline earth metals in amounts ranging from 1 to 2000 ppm. It is known that hydrocarbon streams containing these chloride contaminants, at elevated temperatures and in the presence of water, will hydrolyze to form hydrochloric acid, which, as well known to those skilled in the art, can cause severe corrosion problems to processing equipment.
In a typical refinery the crude is generally first treated in a desalter. The purpose of the desalter is to remove as much of the salts and other water soluble contaminants as possible prior to introducing the hydrocarbon stream, e.g., the crude oil, to the downstream heat exchangers, furnaces, distillation columns, crackers and the associated processing equipment such as pumps, valves, piping and other equipment commonly used in refineries and other petrochemical facilities. It is common for the feed to the desalter to be preheated, generally to a temperature of about 200° to 250° F. After the feedstock has passed through the desalter, which generally operated at a temperature of 200° to 250° F., it passes through a second heating zone operated at a temperature of about 250° to 600° F. The heated stream then passes to a furnace where it is heated to a temperature of 600° to 700° F. The stream is next introduced into an atmospheric distillation column together with steam to make a rough fractionation into generally four cuts: an overhead stream containing light hydrocarbon, e.g., C1 to C8 hydrocarbon, a first intermediate fraction comprising kerosene, jet and diesel fuel, a second intermediate fraction containing gas oil, and a bottoms fraction containing the heaviest components present in the feedstock. As noted, it is common practice to stream strip the crude in the atmospheric distillation, column. Thus, any hydrochloric acid formed upstream of the atmospheric distillation column will be carried over in the light fraction and be condensed with water. Subsequent treatment of this condensed fraction will result in the hydrochloric acid coming in contact with and causing corrosive damage to process equipment used to treat the condensed fraction.
The usual method for dealing with the overhead corrosion resulting from the hydrolysis reaction is to apply neutralizers and corrosion inhibitors. These inhibitors are costly and in many instances cause foaming and deposition problems which can be more damaging than the corrosion problem.